Aromatic polyesters that form optically anisotropic melts and can be melt-spun into oriented fibers are known in the art. For example, U.S. Pat. No. 4,232,144 discloses such polyesters which consist essentially of p-oxybenzoyl units or the 3-methyl or 3-chloro derivatives thereof, 4-oxy-3'-carbonyloxybenzophenone units or the 3-methyl or 3-chloro derivatives thereof, and equimolar amounts of 1,4-phenylenedioxy units and terephthaloyl units. U.S. Pat. No. 4,279,803 discloses such polyesters which consist essentially of substantial amounts of 3- and/or 2-phenyl-4-oxybenzoyl moieties and 4-oxybenzoyl and/or 6-oxy-2-naphthoyl moieties.
It is an object of this invention to provide novel polyesters. Another object is to provide such polymers that form anisotropic melts and that can be melt-spun into filaments which can be heat strengthened to high tenacity. Other objects will become apparent hereinafter.